Effective flash smelting of ore concentrates requires smelting combustion reactions to be carried out as efficiently as possible. A flash smelting furnace typically includes an elevated reaction shaft at the top of which is positioned a burner where particulate feed material and reaction gas are brought together. In the case of copper smelting, the feed material is typically an ore concentrate containing copper and iron sulphide minerals. The concentrate is usually mixed with a silica flux and combusted with pre-heated air or oxygen-enriched air. Molten droplets are formed in the reaction shaft and fall to the settler, forming a copper-rich matte and an iron-rich slag phase.
A conventional burner includes an outer windbox plenum, a water-cooled sleeve, a velocity adjustment cone, and an internal solid fuel injection lance. The burner typically contains a cooling block that is attached to the windbox plenum and integrates with the roof of the furnace reaction shaft.
The lower portion of the adjustment cone and the inner edge of the cooling block create an annular channel. Oxygen enriched combustion air enters the windbox and is discharged to the reaction shaft through the annular channel. The water-cooled sleeve and the internal injection lance create an annular channel within the combustion air flow annulus.
The feed material is introduced from above and descends through the injector sleeve into the reaction shaft inside an internal annulus. Deflection of the feed material into the reaction gas is promoted by a bell-shaped tip at the lower end of the central lance. In addition, the tip includes multiple perforation jets that direct compressed air outwardly to disperse the feed material in an umbrella-shaped reaction zone.
The material feed supply equipment is typically comprised of bins and hoppers, feeders, (e.g., drag-chains, screw conveyors, air slides, vibratory feeders, pneumatic conveyors, etc.), splitter boxes, manifold connectors, and feed pipes located above the injector. Some feed systems combine feed streams of different particle density, shape, and size upstream of the burner.
Known feed systems of this type are associated with disadvantages that can adversely affect the burner performance and cause inefficiencies, such as for example, variable furnace metallurgy and matte grade, poor oxygen utilisation, and increased elutriation of dust to the off-gas handling equipment, etc.
An example of a typical feed problem faced by concentrate burners is poor distribution of feed around the entire circumference of the burner feed outlet. Feed systems usually contain one or more feed chutes that interface with the injector and attempt to utilize splitter boxes and diverter chutes to distribute feed evenly around the circumference. Such systems tend to cause the feed to gather at corners/edges of the chute walls and fins, forming dense “ropes” of feed within the plume, resulting in poor combustion and reduced oxygen efficiency.
Pneumatic conveying systems have been proposed in an attempt to resolve pulsation problems, but require a large investment of capital for new equipment, as well as substantial modifications to existing building layouts to accommodate such systems. These systems, however, do not appear to have improved combustion efficiencies of sufficient order because they feed through intermediate feed chutes, splitters or other equipment which appear to disrupt the particle distribution, and feed through discrete inlet points around the circumference of the burner.
In the burning of other particulate fuels, such as coal burning applications, attempts have been made to achieve the particle distribution with the use of mechanical and rotating machinery. Complex arrangements that extrude pulverized coal into combustion chambers have been investigated in an attempt to eliminate feed pulsations. U.S. Pat. No. 4,803,836 described a typical example of such a device. The same operational problems inherently affect the combustion stability and operation of flash smelters and concentrate combustion reactors.
In this specification, where a literary work, act or item of knowledge (or combinations thereof), is discussed, such reference is not an acknowledgment or admission that any of the information referred to formed part of the common general knowledge as at the priority date of the application. Such information is included only for the purposes of providing context for facilitating an understanding of the inventive concept and the various forms in which it takes.